JSFiddle - React, Tailwind, and code Playground

HTML

<div class="form-group">
  <label class="col-md-4 control-label" for="textinput">Parcelado: </label>

  <div class="col-md-4">
    <div class="radio" onchange="liberar();">
      <label for="radios-0">
        <input type="radio" name="radio" id="radios03" value="Sim"> Sim
      </label>
    </div>
    <div class="radio" onchange="liberar();">
      <label for="radios-1">
        <input type="radio" name="radio" id="radios04" value="Nao" checked="checked"> Não

      </label>
      <p>
    </div>

    <label>
      <input type="text" disabled id="parcela" onkeyup="somenteNumeros(this);" name="parcela" maxlength="2" style="width:50px;" class="form-control input-md"> Máximo 12 parcelas
    </label>
    <p id="saida"></p>
  </div>
</div>

<form name="mespgto">
  <div class="form-group">
    <label class="col-md-4 control-label" for="radios">Meio de Parcelamento:</label>

    <div class="col-md-4">
      <select class="mespgto" id="mespgto" name="financeiro">
        <option disabled selected>Selecione</option>
        <option value="xxx" id="xxx">xxx</option>
        <option value="yyy" id="yyy">yyy</option>
        <option value="www" id="www">Santander www</option>
        <option value="outros" id="outros">Outro</option>

      </select>
    </div>
  </div>
</form>`

JavaScript

window.liberar = function() {

  if (document.getElementById('radios03').checked == true) {
    document.getElementById('parcela').disabled = false
  }
  
  if (document.getElementById('radios04').checked == true) {
    document.getElementById('parcela').disabled = true
    document.getElementById('parcela').value = "";
    document.getElementById('mespgto').disabled=true
    }
  }